Manufacturers of products who ship their goods in a container, such as a box or shipping carton, often desire to apply a label to the outside of the container. The label typically has identifying information, such as product codes, stock or lot numbers, bar codes and shipping data, printed thereon to identify the manufacturer, the contents of the container or the destination of the container. The label has a first side on which the identifying information is printed, and a second side opposite the first side which is coated with a pressure sensitive adhesive. The second, or adhesive, side of the label is applied to the outside of the container so that the identifying information on the first, or printed, side of the label may be read, such as by scanning with an electronic reader.
The label most often used for this purpose is commonly known as linerless label stock because the adhesive side of the label is not protected by a liner coated with a release film. In automated manufacturing facilities that utilize a production line, the label may be mechanically applied to the container when the container is transported on a conveyor to a labeling station. A preferred mechanism for applying the label to the container is a label applicator, also known as a label tamp. The label tamp includes a tamp head that is secured to a tamp head mounting plate on a tamp arm at one end of an axially movable tamp cylinder having an axis of extension that is generally normal to the outside surface of the container on which the label is to be applied. The cylinder may be pneumatic or hydraulic driven, but typically is pneumatic to accommodate the speed of the container along the production line.
With the tamp cylinder retracted, a label is transferred to the tamp head from a label transfer tray coated with a release film, or directly from a printer positioned adjacent the tamp head A stream of air from a blow tube may be directed at the forward face of the tamp head to properly position the label, and a vacuum may be drawn on the tamp head to retain the printed side of the label against the forward face of the tamp head. The tamp cylinder is then extended in the direction of the container until the adhesive side of the label contacts the outside surface of the container on which the label is to be applied, or until the adhesive side of the label is only a slight distance from the outside surface of the container on which the label is to be applied. In the latter case, the vacuum is reversed so that a stream of air is provided to blow the label onto the outside surface of the container from the slight distance.
Label tamps of the previously described type often experience difficulty transferring the label from the transfer tray or the printer to the tamp head and delivering the label to the container. In practice, the label can get caught on the printer or the blow tube as the tamp cylinder is extended in the direction of the container. The adhesive side of the label may come in contact with the printer or the blow tube, for example, if the tamp head and the printer head are not properly aligned or if the tamp cylinder extends towards the container before the label is completely clear of the printer head. The label may also come in contact with the printer or the blow tube if the vacuum drawn on the tamp head is insufficient or irregular.
Assuming that the label is properly transferred to the tamp head and delivered to the container, previously known label tamps operate without difficulty as long as the container is transported to the labeling station of the production line with the outside surface of the container on which the label is to be applied normal to the axis of extension of the tamp cylinder. If the container is transported to the labeling station in a different orientation, the label may not be securely applied to the outside of the container, or worse yet, the label may be wrinkled, and thus unreadable. In the event that a container is improperly aligned with the axis of extension of the tamp cylinder, it may be necessary to shut-down the production line to correct the alignment problem. Naturally, any delay in the operation of the production line results in a corresponding decrease in productivity, and hence profit.
In the case in which the adhesive side of the label contacts the outside surface of the container on which the label is to be applied, it is also possible that the force exerted on the container by the tamp cylinder will exceed the transverse coefficient of friction between the container and the conveyor. This situation is most likely to occur when the production line is alternately utilized for lightweight and heavy containers. If the force exerted by the tamp cylinder is adjusted to apply a label to a heavy container when a lightweight container is transported to the labeling station, that force may exceed the transverse coefficient of friction between the container and the conveyor. As a result, the container may be damaged, or the label may be incorrectly applied as previously described.
As is now apparent, there is a need for a label tamp that transfers and delivers a linerless adhesive label to a container without the possibility that the label will get caught on the printer or the blow tube. Further, there is a need for a label tamp that securely applies a label to a container even if the outside surface of the container on which the label is to be applied is improperly aligned with the axis of extension of the tamp cylinder.
In particular, there is a need for a label tamp that delivers a linerless adhesive label to a container and securely applies the label to the container without wrinkling the label even if the outside surface of the container on which the label is to be applied is improperly aligned with the axis of extension of the tamp cylinder. It is also apparent that there is a need for a label tamp that applies a linerless adhesive label to a lightweight container without exceeding the transverse coefficient of friction between the container and the conveyor.